Alpha substituted unsaturated aldehydes having the structure: ##STR2## wherein one of the dashed lines is a double bond and the other of the dashed lines is a single bond; wherein R.sub.1 is allyl or benzyl, R.sub.2 is one of alkyl, aryl, alkenyl or alkoxyalkyl and R.sub.3 and R.sub.4 are each hydrogen or alkyl, with the proviso that when R.sub.3 is alkyl the dashed line between the .beta. carbon atom and the .gamma. carbon atom represents a double bond and when R.sub.3 is hydrogen, either of the dashed lines is a double bond, are valuable substances useful in the formulation of perfumery, tobacco and food flavoring materials, in the preparation of polymers and as intermediates for the preparation of pharmaceutical substances.
German Pat. No. 1,244,784, issued on July 20, 1967, discloses the reaction: ##STR3## wherein R can be one of alkyl, alkenyl, allyl, propargyl, cyclohexyl or benzyl; X is chloro or bromo and R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 can be hydrogen, alkyl, alkenyl or phenyl. The reaction of the German Patent is limited to ketones. Although such ketones could be unsaturated, the nature of the reaction is different in kind from the reaction of the instant invention.
De Graff, et al, Tetrahedron Letters, 17, pages 1653-56, 1974, teaches that both 1-cyclohexene carboxaldehyde and 2-methyl-2-pentene-1-al could be converted into their respective anions by reaction with a small excess of potassium amide in liquid ammonia at -60.degree. C and that treatment of these anions with reactive alkylating agents gives moderate to good yields, according to the following reaction scheme:
__________________________________________________________________________ SCHEME A __________________________________________________________________________ ##STR4## ##STR5## ##STR6## ##STR7## alpha-alkyl(2a,b) beta-alkyl(3a,b) gamma-alkyl(4a,b) a:R.sub.1 R.sub.2=(CH.sub.2).sub.3 b:R.sub.1 =R.sub.2=CH.sub.3 __________________________________________________________________________
Whereas the reaction of the instant invention is commercially feasible, the De Graff, et al. reaction, taking place with potassium amide in liquid ammonia at a very low temperature, gives rise to a reaction system having little commercial feasibility and gives rise to a mixture of products.
Chemical Abstracts, 135501 g, 1974, summarizes a paper by Tsukasa, et al. entitled: "Alkylation of alpha, beta-unsaturated cyclic ketones. Synthesis of jasmones". In this case cis and trans jasmones are synthesized by reaction of 3-methyl-2-cyclopentenone with an alkyl halide in the presence of powdered potassium hydroxide and dimethyl sulfoxide; the Chemical Abstracts synthesis being carried out with dimethyl sulfoxide on a ketone rather than an aldehyde. This process is different in kind from the process of the instant invention.